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Prius Prime Regeneration Braking Efficiency Experiment

Discussion in 'Prime Technical Discussion' started by erikrocketman1, Jun 1, 2018.

  1. erikrocketman1

    erikrocketman1 New Member

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    I haven't seen any posts on regeneration efficiency, and wanted to do my own experiment. Pictures below.

    Bought a Prius Prime (Plug-in Hybrid w/ 6kW reserved for eV mode only) last week and naturally needed to nerd out with it!

    Took a vacation in Lake Arrowhead, California this Memorial day Weekend. Used this opportunity to calculate the regeneration efficiency of the Prius Prime by seeing how much energy it recharges to the batteries from the top of the mountain to the bottom.

    Using the elevation difference, and the total weight of the car with luggage and passengers, found that the regeneration efficiency to be about 51%, regenerating 3.22 kWh back to the battery from a 4400 ft altitude.

    Driving 110 miles the whole day and only used 0.65 gallons of gas! Car was at 100% battery at beginning of day, going down the mountain, I was at ~42% battery before descending the mountain, and managed to top of exactly at 100% at the bottom of the mountain). 169 mpg!

    Please share your stories!
     
  2. bisco

    bisco cookie crumbler

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    welcome, beautiful!(y)
     
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  3. PlugmeInplz

    PlugmeInplz New Member

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    Its cool how you calculated this. What is interesting is the prime charged to 100% at the bottom of the hill, so the prime will not accept any more charge and brakes will absorb the excess energy. If you drained the battery at the top you could of potentially gotten an even larger charge increasing the regen efficiency. Great MPG
     
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  4. PlugmeInplz

    PlugmeInplz New Member

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    What was you EV to HV ratio?
     
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  5. Roy2001

    Roy2001 Active Member

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    Great information!
     
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  6. bisco

    bisco cookie crumbler

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    stickied!(y)
     
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  7. erikrocketman1

    erikrocketman1 New Member

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    Actually, I got really lucky and hit 100% right before entering the freeway at the bottom of the hill, so no brake pad was used at all the whole way down!

    The entire 110 mile journey was about 69% EV driving ratio!
    HV mode didnt turn on until the last ~34 miles of my journey. Also, I didn't go into "B" mode down hill, for some reason it kicked on my engine.
     
    #7 erikrocketman1, Jul 19, 2018
    Last edited by a moderator: Jul 20, 2018
  8. Prime Objective

    Prime Objective Junior Member

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    If you do not want to use the ICE just switch back to "D" before stopping or accelerating.
    For an explanation of "B" mode Go to wiki books and search the following - Toyota Prius/Driving tricks
     
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  9. axle2152

    axle2152 Active Member

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    Nice to know that you can regenerate like that. One question is suppose you deplete the battery in EV and switch to HV and start going down a mountain where you can regenerate a lot, say 3kW or enough to be able to gain a good bit of EV range, would you be able to enter EV mode again? I think this was something the Volt cannot do (I watched a video of Volt owner shutting his car off to restart it to be able to use EV mode after regenerating down a mountain).
     
  10. CraigCSJ

    CraigCSJ Active Member

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    The answer for Prime is that after regenerating awhile the car showes between 1 and 2 miles of EV available and at that time EV driving is available. It may automatically switch to EV driving at that time.
     
  11. lili220

    lili220 New Member

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    will absorb the excess energy. If you drained the battery at the top you could of potentially gotten an even larger charge increasing the regen efficiency. Great MPG
     
  12. JoyJonson

    JoyJonson New Member

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    Thanks for info))

    I fount info what I needed

    I would like to know feedback about Toyta Camry LE;);)
     
    #12 JoyJonson, Dec 13, 2018
    Last edited by a moderator: Dec 13, 2018
  13. JoyJonson

    JoyJonson New Member

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    :):):)сool
     
  14. montreal

    montreal Junior Member

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    Excellent data. Thank you for posting it.

    It is worth keeping in mind that the calculations ignore parasitic losses. When ever a vehicle coasts (uphill, downhill or on level ground), it losses significant energy to aero drag and rolling resistance. That energy is gone and cannot be recaptured by regen.

    Actual wheels to battery efficiency is probably close to motor efficiency, so 70-80%?
     
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  15. kepani

    kepani Member

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    Subscribed! I love this kind of stuff...the nerd in us! :ROFLMAO:

    Thank you for sharing this!
     
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  16. Andyprius1

    Andyprius1 Senior Member

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    On my daily return, the car is low on charge, I have on petty good series of upgrades, so I charge to somewhere between 15-20 mpg, use most of that until the last peak. At the light I start charging again, conservatively until the actual downhill roll starts. At that point I use either drive or Brake. Both positions
    provide very small, even non existent ICE usage and gravity charges most of that portion until the bottom of the American River canyon. All basically Brake charging. The EV use is generally 65-69% Now the uphill starts, a more dangerous portion so my average speed is definite less than 30 MPH. Until the next peak, then it’s EV for the rest of the commute. I generally make it home with 5-9 miles left. I consider that a failure, I’d rather run out at my driveway. Well, next time ... maybe.
     
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  17. chogan2

    chogan2 Senior Member

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    I can take a rough cut at showing that, based on amperage required to drive a steady 55 MPH on level highway. I estimate that to be 35 amps, using a Scangauge, Presumably, that's the frictional losses when driving at 55 MPH, plus motor/inverter losses.

    From that, I can adjust out the friction losses, like so, for an assumed 55 MPH or (guesstimated) 65 MPH 8 mile trip:

    upload_2023-2-16_12-1-2.png

    And it's exactly as you said. If the motors are about 80% efficient, and you lose about 10% of the energy when you charge the battery (per https://fueleconomy.gov/feg/atv-ev.shtml), you ought to see about 70% of potentially recoverable energy end up in the battery. And that's just about how it all works out, starting from an observed 35 amps to keep the car moving along steadily at 55 MPH.
     
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